The present invention relates to variable capacity compressors for use in heat-exchange circuits including evaporators, of air conditioning systems.
A variable capacity compressor is known, e.g. from Japanese Provisional Patent Publication (Kokai) No. 61-215468, in which pressure within a low pressure chamber of the compressor is detected, and a pressure-responsive valve is operative in response to the detected pressure to bring the low pressure chamber and a pressure-controlled chamber into or out of communication with each other, thereby varying the delivery quantity or capacity of the compressor. When a vehicle compartment, for example, is cooled by an air conditioning system employing such internally controlled variable capacity compressor, it takes a considerably long time unitl the vehicle compartment is cooled down, because the temperature of an evaporator of the air conditioning system drops in such a manner as to gradually approach a set value as indicated by the broken line A' in FIG. 2. The reason for this is that since the cooling load is large at the start of operation of the air conditioning system, the flow rate of the refrigerant gas is so large that pressure loss occurs between the evaporator and a suction chamber of the variable capacity compressor. That is, the pressure within the suction chamber drops due to the pressure loss, resulting in a drop of the pressure within the low pressure chamber. As a result, the pressure-responsive valve is operated in response to the pressure drop to reduce the delivery quantity or capacity of the compressor. In particular, if a connection line between the evaporator and the suction chamber of the compressor is long in distance, the temperature drop of the evaporator is slow, so that the vehicle compartment is not rapidly cooled down after the air conditioning system is started.